1. Field of the Invention
This invention relates to a process for controlling pitch deposition from pulp in papermaking systems.
2. Description of the Prior Art
Pitch deposition can be detrimental to efficient operation of paper mills. Pitch can deposit on process equipment in papermaking systems resulting in operational problems in the systems. Pitch deposits on consistency regulators and other instrument probes can render these components useless. Deposits on screens can reduce throughput and upset operation of the system. Deposition of the pitch can occur not only on metal surfaces in the system, but also on plastic and synthetic surfaces such as machining wires, felts, foils, uhle boxes and headbox components. Pitch deposits may also break off resulting in spots and defects in the final paper product which decrease the paper's quality.
Surfactants, anionic polymers and copolymers of anionic monomers and hydrophobic monomers have been used extensively to prevent pitch deposition of metal soap and other resinous pitch components. See "Pulp and Paper", by James P. Casey, Vol. 11, 2nd edition, pp. 1096-7. Bentonite, talc, diatomaceous silica, starch, animal glue, gelatin and alum are known to reduce pitch trouble. U.S. Pat. No. 3,081,219, Drennen et al., discloses the use of a polymeric N-vinyl lactam to control pitch in the making of paper for sulfite pulps. U.S. Pat. No. 3,154,466, Nothum, discloses the use of xylene sulfonic acid-formaldehyde condensates and salts thereof as pitch dispersants in papermaking. The use of napthalene sulfonic acid-formaldehyde condensates for pitch control is also known in the art. U.S. Pat. No. 3,582,461, Lipowski et al., teaches the use of water soluble dicyandiamide-formaldehyde condensates to control pitch. U.S. Pat. No. 3,619,351, Kolosh, discloses process and composition for controlling resin in aqueous cellulose pulp suspensions which comprises incorporating in the suspension a resin control agent comprising a certain water-soluble nonsurface-active cationic quaternary ammonium salt.
Additionally, U.S. Pat. No. 3,748,220, Gard, discloses the use of an aqueous solution of nitrilotriacetic acid sodium salt and a water soluble acrylic polymer to stabilize pitch in paper pulp. U.S. Pat. No. 3,992,249, Farley, discloses the use of certain anionic vinyl polymers carrying hydrophobic-oleophilic and anionic hydrophilic substituents when added prior to the beating operation in the range of about 0.5 part to 100 parts by weight of the polymer per million parts by weight of the fibrous suspension to inhibit the deposition of adhesive pitch particles on the surfaces of pulp-mill equipment. U.S. Pat. No. 4,184,912, Payton, discloses the use of a 3-component composition comprised of 50-20% by weight of a nonionic surfactant, 45-15% by weight of an anionic dispersant, and 45-15% by weight of an anionic polymer having molecular weight less than 100,000. U.S. Pat. No. 4,190,491, Drennen et al., discloses the use of a certain water-soluble linear cationic polymer having a viscosity average molecular weight of about 35,000 to 70,000. Also, U.S. Pat. No. 4,253,912, Becker et al., discloses the use of a certain soluble, chlorine-resistant phosphonate of high calcium tolerance to disperse pitch contained in the aqueous medium of a pulp or papermaking prpcess.
This relates to a process for controlling pitch deposition from pulp in papermaking systems which comprises adding to the pulp an effective amount of a polymer having methyl ether groups pendant to the backbone of the polymer. The polymer can be a water soluble homopolymer of methyl vinyl ether. The polymer can also be a water soluble copolymer derived from polymerizing methyl vinyl ether with nonionic hydrophilic monomers, anionic hydrophilic monomers and/or nydrophobic monomers, wherein the copolymer has at least 20 mol percent of methyl vinyl ether.
In another aspect, this invention comprises adding to the pulp an effective amount of a water soluble polymer derived by substituting methyl ether groups onto a preformed reactive polymer, such as polyvinyl alcohol or cellulose, wherein the water soluble polymer has from about 20 percent to about 100 percent of the available reactive groups of the preformed reactive polymer substitued with methyl ether groups. Preferably, the water soluble polymer is a water soluble cellulose ether. More preferably, the water soluble cellulose ether is selected from the group consisting of methyl cellulose, methyl hydroxyethyl cellulose, methyl nydroxypropyl cellulose, carboxymethyl methyl cellulose, and methyl hydroxybutyl methyl cellulose.
There are several advantages associated with the present invention as compared to prior art processes. These advantages include: an ability to function without being affected by the hardness of the water used in the system unlike certain anionics; an ability to function with lower foaming than surfactants; and an ability to function while not adversely affecting sizing, fines retention, or pitch retention.